Hi, In your tutorial/t7.geo, you defined Attractors. Can you tell me the meaning of expressions on the right hand side of the following definitions: Attractor Point{1} = {0.01, 0.01, 2}; Attractor Line{5} = {0.3, 0.01, 2}; Attractor Line{7} = {0.1, 0.02, 8}; Thanks, Jin